The present invention relates to a line-spacing system for a typewriter or other printing office machine, adapted to operate without return of the carriage to the beginning of the printing line in a machine wherein a single control device actuates a line-spacing mechanism of the machine and effects return of the carriage to the beginning of the print line as defined by a left-hand margin stop.
Line-spacing systems for office machines are known wherein the line-spacing mechanism of the platen is controlled by a lever disposed at one end of the carriage and connected to one end of a belt which can be wound on a reel controlled by a corresponding return-to-the-beginning clutch. Upon the actuation of the return-to-the-beginning clutch and the escapement tooth being withdrawn from the rack, the line-spacing control lever is actuated for the rotation of the platen and, thereafter, the carriage is shifted to its left-hand margin. The clutch, therefore, acts as a single control for both the line-spacing and the return-to-beginning operations. The margin stop then produces the reopening or disengagement of the clutch, the re-engagement of the escapement tooth and the return of the line-spacing lever in the initial position of the carriage. Though these systems are fairly simple and reliable, they cannot be used to effect line-spacing without returning to the beginning of the printing line.
A system for line-spacing without return of the carriage to the beginning of the printing line is known wherein the line-spacing control is achieved by actuating an auxiliary electric motor connected through a toothed belt and two gears to the platen of the machine. This system requires the use of a second electric motor and is, therefore, costly.
A second system for line-spacing without return of the carriage to the beginning of the printing line is known wherein the electric motor of the machine produces the rotation of a cam in the path of which a corresponding lever is positioned upon depression of the line-spacing key. The lever is thus shifted and, through the medium of a vertical hook supported by the frame of the machine, causes a transmission shaft disposed on the carriage parallel to the platen to rotate. The shaft actuates the corresponding line-spacing mechanism via a connecting rod. The return to the beginning of the printing line which is controlled by the same machine motor, also operates a line-spacing mechanism with return to the beginning, of the type already described. This line-spacing system without return to the beginning, which is added to that associated with return to the beginning, is therefore rather costly and complicated.
A third line-spacing system is known wherein a cable fixed to one end of the carriage is stretched over the entire length of the carriage and winds around a pulley fixed at the other end of the carriage. The cable passes between two rollers, mounted on a Y-shaped arm fixed to the frame of the machine, and between a roller mounted on an actuator disposed between the two rollers on the arm. By acting on a key connected to the actuator, the cable is tensioned and rotates a lever on which is pivoted a pawl adapted to engage a ratchet wheel on the platen. With this system, there is the disadvantage that the cable slackens with use and therefore line-spacing control no longer conforms with the desired amount. The dimensions of the Y-shaped arm require a carriage of dimensions larger than those of the platen and, finally, in this system, there is also necessary a mechanism for return to the beginning and for line-spacing with return to the beginning of the printing line which is independent of the above-mentioned system.